

It can saturate the MacOS VideoToolBox framework, causing FCPX to crash. Make sure you are not running the Chrome browser or any other browser based on Chrome. That is fairly old but I don't remember seeing this problem on those versions. You are running FCPX 10.3.4 on High Sierra 10.13.6. I do not have the option to get to Settings. FCPX crashes right after I select: File>Share>Master File. Thanks! I have background rendering disabled. IOW remove Fx from 1/2 of the timeline, then 1/4, then 1/8, etc until you find it, then examine the effect or plugin used on that range. If it exports OK with no effects, then use the similar "half splitting" method on an effect-laden timeline to narrow down what timeline range has the plugin causing the crash. If that works try the other 1/2 of the timline, then 1/4, then 1/8, etc until you narrow down where the problem is.

If it fails, then delete 1/2 of the timeline, and try to export that. If any of those fail, duplicate the timeline as a snapshot, open that and strip out all effects with Edit>Remove Effects.

If that works then try exporting this way: File>Share>Master File>Settings, Format: Computer, Video Codec H.264 Faster encode, Resolution: 1920x1080. The ProRes output will be very large but it's only for a test. This helps distinguish between an export problem vs a Long GOP encoding problem. File>Share>Master File>Settings, Format: Video and Audio, Video Codec: Apple ProRes 422. This helps segregate the render phase vs the encode phase. Then delete all render files, then select all clips in the timeline with CMD+A, then render them with CTRL+R.

In addition to what said, make sure you have background rendering disabled. Nothing is working and FCPX just keeps crashing on Share. I have reinstalled FCPX, trashed preferences, trashed Libraries, created new Libraries with new clips, run Disk Utility, repaired permissions, restarted the computer, etc. FCPX 10.3.4 crashes during File>Share>Master File.
